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In this clip from the 2005 presentation “Impacts of Changes in Extreme Weather and Climate on Wild Plants and Animals,” biologist Camille Parmesan explains how warming climates may be leading to a change in genetic ratios in populations of Edith’s Checkerspot Butterfly. In populations that have successfully settled in new areas (dispersers), more of the butterflies had high ATP and large flight muscles than did populations that had lived in the same area for a long period of time. In response to a question from the audience, Dr. Parmesan explains that although populations may evolve to be better dispersers over the short term, because dispersers have low reproductive rates, the ratio of dispersers to sedentary individuals will likely shift again once a new population has been established.
Population genetics are studied by observing visible physical characteristics of individuals in a population or by analyzing cells to search for a specific genetic sequence.
Studies such as Dr. Parmesan’s require on-the-ground observation and, sometimes, capture of butterflies in remote mountain locations. Because she needed to be able to compare her own results with previous observations of populations similar to or the same as those studied by others, Dr. Parmesan’s ground study locations were determined by where she had data from previous experiments.
Scientific data suggests that the climate is warming. In both apparent and subtle ways, these changes in average temperature will impact where certain species are able to survive. Studies such as Dr. Parmesan’s suggest that some species may be able to adapt or evolve on a population level in order to survive these changes. Understanding which species are likely to be able to survive on their own and which are at risk for extinction is important for scientists and decision-makers who want to preserve biodiversity.
Reflect on the clip using these questions. Then, record your thoughts in a science journal or discuss them with a friend.
Modeling population-level evolution
Imagine a butterfly population that lives in an area where spring conditions now occur too early for caterpillars to survive well. What will the genetics of this population look like next year?
Materials: Notebook, paper and pencil or dedicated computer file where you can keep your work.
a.) Over the course of history, some human populations have been more dispersive while others have been more sedentary. What are some of the pressures that might drive a human population to leave one area and colonize another?
b.) Imagine and describe a radical climate change that could occur where you live (shorter winters, less rain, more storms, ect.). Is it better to stay where you are or move to a new location? Why?
c.) What causes most shifts in genetic variation (evolution)?
Parmesan, C., T.L. Root & M. Willig. Impacts of extreme weather and climate on terrestrial biota. (2000) Bull. American Meteorological Soc. 81: 443-450.
A complete video of Dr. Parmesan's public lecture on this same topic is available on agci.org.